Parallel screw machinist&#39;s clamp



April 29,4 1952 R. A. MULL. 2,594,794

Y PARALLEL SCREW MACHINISTS CLAMP Filed June 25, 1947 2.9 Z0 /0 30/ l /2 ll *MMM` t f/ (a Ma, ZW

Patented Apr. 29, 1952 Stdt UNITED STATES PTEN' FFICE 2,594,754 emitter; sciaiw MAcinNIses essere nayinan. thin, st.. Joseph 'roti/lisais,

Berren County,

Mich.

replicates ruse 25, 1947; lsaai' Nt. 753,965

1 This invention relates to' improvements in niachinists clamps. y y

Conventional machinists clamps'have parallel clamping bars or jaws and a pair'of screws one of which extends freely through one'ot the bars adjacent to the clamping end thereof and is threaded through the other of theY harsv adjacent to its clamping end while the remaining screw is threaded through the heel portion of the second bar and is in endwise engagement within a socket in the rst bar. The rst screw is used for effecting preliminary clamping and the second screw for tightening the clamp..` K 1 A very serious disadvantage of prior machinists clamps has resided in that the handle portions of the screws extend in opposite directions from the clamp assembly, that is, one extends from one side of one of the bars and the other extends from the outer side of the other vof the bars thereby requiring that the clamp be well elevated above a surface over which it is to be used or that the screw containing portion o' the clamp hang over the edge of such surface invorder to clear the projecting handle portion of the downl wardly extending screw.

An important object of the present invention is to provide a machinists clamp whichinguse is adapted to rest directly upon a ASupporting surface without any interference from the clamp screws.

Another object of the invention is to provide a machinists clamp in which. the handle portions of both of the screws extend in the same direction beyond the same clamping bar or jaw.

Still another object of the invention is toprovide a machinists clamp in which one ofthe bars can serve as a base directly engageable vupon a supporting surface such as a machine table and with the work gripped in the clam'p directly in position for machining operation thereon.

A further object is to provide a machinists clamp which in addition to serving as a clamp also is adapted to function as a work support.

A still further object of theinvention is to lprovide a machinists clamp having novel distortion or deiiection relief structure.

An additional object of the invention is to provide a novel arrangement of the clamping screws inamachinists clamp. t

Other objects, features andadvantagefs'o'f, the present invention will be readily apparent4 from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings, in which:

Figure 1 is a side elevational view of a ma- 1 claim. (ci. 1444300) chinists clamp embodying the features of the present invention.

Figure 2 is a top plan View showing a pair of the machinists clamps in use on a work piece.

Figure 3 is an enlarged side elevational View, partiailyin section, showing certain details of structure ci the clamp.

Figure 4 is a fragmentary bottom plan View of the clanflp.` A,

if; machinists clamp in according to the present invention departs radically from conventional machinists clamps by having a base bar I i which is adapted to rest without obstruction freely upon a surface 2 which may comprise a work table of r etal working machine, or the like. To the attainment of this novel end, an upper clamping har i3 is clamphigly associated with the base har ii through the medium of clamp screws It andl which are threaded through appropriate respective tapped apertures Il and I in the clampv har i3 have only their ends associated with the base har Il. Thereby the screws lll and i5 extend only beyond the outer side of the clamping b'ar i3 and the outer side or base face identiiedat i9 of the base bar Il is left entirely free to rest directly upon the surface l2 over the entire area of the lower or base surface i9 of the hase bar.

By preference the base bar H is somewhat longer than the clamping bar I3 so that with the bars in parallelism and with the heel ends thereof disposed generally coplanar, the forward end portion or" the base bar Il extends substantially beyond the end of the clamping bar i3. Thereby a substantial base extension is provided for supporting a workpiece 2Q or a pair of woripieces 2t with a iullfbvearing.

The upper-lor clamping bar t3 may have the jaw end portion thereof beveled as indicated at 2lv on its upper or' outer surface, in conventional manner.

serves to run the liminary to the nal tightening, does not extend through the base bar II but is freely rotatably retained therein in a novel manner. To this end, the extremity of the screw I4 which is associated with the base bar I I is formed or otherwise provided with a larger diameter extremity ange 22 which in the assembly is opposed by a counterbore shoulder 23 at the inner end of a bore 24 through which the extremity portion of the screw I4 passes (Fig. 3) The flanged tip of the screw is retained against dropping out of the countercore by suitable means such as a retainer plate 25 removably secured retainingly across the counterbore as by means of a screw 21, a recess 28 being provided to sink the retainer plate 25 and the screw 21 up within the base bar II entirely clear of the base surface I9. Through this arrangement, the retainer plate 25 supports the screw I4 and thereby also the clamping head end of the clamp bar I3 when the same is idle, and when the clamp is in use, the fiange 22 of the screw engaging the shoul v`er 23 draws the base bar II into clamping engagement with the clamp bar I3 which is threadedly run toward the base bar by operation of the screw I4.

Where the retainer flange 22 on the screw I4 is formed integrally with its extremity, a manually engageable, preferably knurled head 29 at the opposite extremity of the screw is preferably formed separately and may be provided with a tapped axial bore 39 into which the upper extremity of the screw I4 is threaded and within which it may be pinned against loosening as by means of a drive pin 3l. A conventional turn bar transverse hole 32 may be formed in the head 29.

The tightening screw I5 may be of substantially conventional construction and operation. Therefore it has formed at its upper end with a preferably knurled finger engageable head 33 having a turn bar transverse opening 34 therethrough. At its lower end the screw I5 is formed with a non-threaded bearing extremity portion 35 which is freely rotatably received in an upwardly opening socket 31 in the base bar I I.

In the operation of the clamp I the bars II and I3 are separated by appropriately turning the screw I4 until the work 28 can be received therebetween. Thereafter the screw I4 is turned in reverse to run the clamp bar I3 down onto the work, the screw I being thereupon run down through its threaded bore I8 in the bar I3 until the bearing tip 35 drives into the socket 31 and tilts the clamping head of the bar I3 into tight clamping engagement with the work.

Inasmuch as the work is often of necessity clamped quite tightly, there may be a tendency of the clamping bars II and I3 to spring at least slightly apart at their heel end portions.

In the upper clamping bar I3 such springing will be of no consequence. However in the base bar II downward springing of the heel end thereof would have a tendency to tilt the intermediate portion of the bar, that is the effective clamping portion thereof upwardly and thus throw the work 28 out of true with respect to the surface I2.

In order to avoid any tendency to such possible deviation out of true due to flectional distortion of the base bar II, the heel end portion thereof is undercut as indicated at 38 to provide a liberal relief or clearance deflectional distortion so surface I9 will at all times remain true and flush with the surface I2. It will be observed that the relief clearance 38 extends from approximately that the base bearing to compensate for any 7 the axis of the preliminary tightening or rundown screw I4 to the heel extremity of the base bar II, since the defiectional distortion will occur only in the area between the two screws since the screw I4 is pulling the base bar I I toward the clamping bar I3 while the iinal tightening screw I5 is pushing the base bar II away from the clamping bar I3.'

In practice, matching pairs of the clamps I0 are provided wherein the base bars II are ground so as to be accurate mates. This means that both the base bearing surfaces I9 and the top work supporting surfaces of the bars II of the mated pairs are finished or ground together so that the work 28 will be supported quite accurately parallel to the surface I2 by the base bars Ii.

By having the forward ends of the base bars I I extend substantially beyond the actual clamping portions of the base bars a thorough, complete support is afforded for the work 28. This is well illustrated in Figs. 1 and 2.

It will, of course, be understood that various details of construction may be Varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claim.

I claim as my invention:

In a machinists clamp adapted to be paired with a matched companion clamp to combine the functions of clamp and parallel bar in supporting a work piece with parallel precision upon a machine table, a base bar, a clamping bar, and respective thrust and tension screws threaded through the clamping bar and having their lower ends in freely rotatable operative engagement with the base bar above the lower surface of the base bar and cooperative to effect a clamping interrelationship upon a workpiece between the bars, the thrust screw being located in the heel portions of the bars and the tension screw being spaced forwardly from the thrust screw, the base bar in the work-supporting portion thereof forwardly of the tension screw being about twice as long as the portion of the base bar from the tension screw to the heel end of the base bar, said work-supporting portion having the upper and lower surfaces thereof parallel, the lower surface of the base bar from at least the axis of the tension screw and thence rearwardly under the thrust screw to the extremity of the base bar being undercut to clear the same from and avoid contact with the machine table and thus prevent thrust and tension distortions in the screwengaged portion of the base bar in tightening the bars against a work piece from disturbing the parallel precision of the forward lower surface of the base bar relative to the machine table.

RAYMOND A. MULL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 169,027 Naumann Oct. 19, 1875 174,838 lNaumann Mar. 14, 1876 893,831 Adams July 21, 1908 922,336 Rivers May 18, 1909 1,214,521 Dosch Feb. 6, 1917 1,713,239 Parkhurst May 14, 1929 

